Disclosed herein are hand held photochromic marking implements and methods for making the same. More specifically, disclosed herein are hand-held marking implements that include a handle portion for gripping the marking implement, and a marking portion comprising a solid carrier material and a photochromic colorant. In one embodiment the photochromic colorant is substantially colorless when inactivated and a predetermined color when activated. In another embodiment a method is provided forming a hand-held marking implement. This method can comprise forming flowable solid carrier material including a photochromic colorant cooling and shaping the flowable carrier material. In this way a solid hand-held marking implement as described above can be formed.
In general, hand-held marking implements can have many structural forms and utilize many direct marking modes. The typical structure of a marking implement is a variation on an elongated, stick-like form, which facilitates controlled marking by the human hand. The common direct marking modes include deposition of either colored liquid substances, such as an ink, or colored solid phase substances, such as a graphite, chalk, or wax, onto a recording media. Marking implements comprising a colorant incorporated into a solid carrier of wax or chalk are commonly referred to as crayons. Crayons are in the solid phase at ambient temperature, but are soft enough to deposit colored carrier material directly onto a selected media.
Photochromism in general is a reversible change of a single chemical species, a photochromogen, between two states having distinguishably different absorption spectra, wherein the change is induced in at least one state by the action of electromagnetic radiation. The inducing radiation, as well as the changes in the absorption spectra, are usually in the ultraviolet, visible, or infrared regions. In some instances, the change in states is thermally induced. The photochromogen can be a molecule or an ion, and the reversible change in states may be a conversion between two molecules or ions, or the dissociation of a single molecule or ion into two or more species, with the reverse change being a recombination of the two or more species thus formed into the original molecule or ion. Photochromic phenomena are observed in both organic compounds, such as anils, disulfoxides, hydrazones, osazones, semicarbazones, stilbene derivatives, o-nitrobenzyl derivatives, spiro compounds, and the like, and in inorganic compounds, such as metal oxides, alkaline earth metal sulfides, titanates, mercury compounds, copper compounds, minerals, transition metal compounds such as carbonyls, and the like. Photochromic materials are known in applications such as eyeglasses, toys, clothing, and inks. Photochromic phase change ink compositions are described in U.S. Pat. Nos. 5,593,486 and 5,759,729, which are incorporated herein in their entirety by reference.
A need remains for improved hand-held direct marking implements which, unlike conventional marking implements, have photochromic characteristics. These characteristics can provide, for example, the ability to create marks that either become visible or change color state upon activation. A need further remains for marking implements having compositions and structural shapes designed to be hand-held and capable of directly marking various recording media with a mark having a modifiable visual appearance. There is an artistic need for a hand-held, direct-to-media marking implement that can create a mark that can be reversibly modulated between a first color and a second color. There is also a need for a simple, hand-held direct-to-media marking implement which enables the quick placement of a marking on a medium which is not readily detectable until it is activated by a radiation source.